I. Field of the Invention
The present invention relates to the forming of a tubular beam and more particularly to a one-piece tubular beam.
II. Description of the Art
Vehicle doorbeams are widely used in the automotive industry to enhance the impact strength of vehicle doors and thereby to enhance passenger safety. Typically these beams are fabricated from multiple pieces including a metal tube and brackets welded on the opposite ends of the tube. The brackets are used in securing the beam within the door frame. Such beams are not without their drawbacks. First, the multi-piece beams require numerous manufacturing steps, and therefore are relatively labor-intensive and expensive. Second, the structural integrity of these doorbeams greatly depends on weld consistency and weld quality. Third, any welding splatter left on the beam may cause a squeak if the splatter contacts another interior door component.
The doorbeams also can be manufactured as a single-piece or one-piece beam. A method for roll-forming such a beam is illustrated in U.S. Pat. No. 5,756,167 issued May 26, 2998 to Tamura et al. The Tamura process rollforms continuous strip stock into one-piece beams using specially designed rollers. The rollers have a circumference that corresponds to the length of the beam. The rollers create alternating rolled body portions and flat end brackets joined together by curving transition portions. This process also is not without its drawbacks. First, the tooling is extraordinarily expensive. Second, the separate set of tooling is required for each doorbeam. Third, extensive set up time is required when a new/different doorbeam is to be manufactured. As part of the set up, different circumference rollers require different distances between the axes of opposing and adjacent rollers.
One-piece beams also can be manufactured using stamping or pressing methodologies. Examples of such processes are illustrated in U.S. Pat. No. 5,183,718 issued Sep. 29, 1998 to Masuda et al and Japanese Patent Publication 4-238725 published Aug. 26, 1992. These methods form individual metal blanks into beams, and also are not without their drawbacks. First, these methods are relatively labor intensive resulting in relatively high manufacturing costs because individual blanks must be press formed. Second, stamping often utilizes less of the sheet than rollforming, thereby creating more waste. Third, different doorbeams require different tooling.
The aforementioned problems are overcome in the present application wherein a one-piece doorbeam is rollformed from continuous stock using relatively simple tooling and producing relatively little waste. More specifically, the process includes the steps of removing material from the edge of a continuous metal stock at spaced locations, rollforming the entire stock into a tubular shape so that the opposite edges engage one another except where material has been removed, welding the engaged edges, severing the tubular shape in the area where material was removed to create a rollformed piece having two ends, and opening at least one of the ends to create an end bracket.
The present invention has a variety of advantages over the prior techniques. First, highly specialized and unique tooling is not required. Second, virtually any length doorbeam can be created using a single set of tooling. Third, the integral end brackets can be uniquely shaped and processed following the basic forming steps. Consequently, the present invention is relatively labor efficient and inexpensive. Further, the quality and consistency of the tubular beam is improved.
These and other objects, advantages and features of the invention will be more fully understood and appreciated by reference to the detailed description of the preferred embodiment and the drawings.